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Buying Keysight 34461A 6.5 Digit Bench DMM - Opinions?

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J-R:
The 34465A is a no-brainer compared to the 34461A with the promotion and those features like the thermocouple support and extra current and resistance ranges.  From a price perspective, the 2M memory upgrade is worth about $300 and would add some value to the instrument, and the U1733C retails for about $550 and can be sold on eBay for $400 or more if necessary.  Either are good options depending on your needs.

tszaboo:
We have both in the office. The 34461A is a good meter. If you can afford an update to the 34465A, you are golden.
The DMM6500 is OK, but it has some issues that gets on my nerves every time I want to do more than measure a value. No cold junction compensation for thermocouple. The battery dies in like 2 years, you have to take it apart a lot to replace it. The buffering somehow makes an excel starting the middle of the buffer. Sampling settings are unintuitive.
The only two things going for the DMM6500 IMHO are the high speed sampling, and the optional scanner card. If you don't need those, I would get the 34461A. Even though there was 1 out of 4 or 5 that died on me, it was replaced in warranty.

Caliaxy:

--- Quote from: Kleinstein on March 06, 2024, 08:44:33 am ---
--- Quote from: Caliaxy on March 06, 2024, 04:07:50 am ---Not sure if relevant to you, but be aware that 34661A doesn’t take thermocouples of any kind.

--- End quote ---
With most DMMs the use of thermocoules is limited, as the connector and cold junction temperature compensation don't work well. So don't expect much accuracy.
An exception is the Keithley 2110, with a proper TC connector.

--- End quote ---

Spot on, educational as always!

I only wanted to point out that 34661A can't read thermocouples, whereas both DM6500 and 34665A (34661A's bigger brother) can.

Why would one use a 6.5 DMM (with a dc voltage accuracy in the vicinity of 30 ppm) with a thermocouple of 1-3% accuracy? Not necessarily for accuracy per se (or lack of it...), but also for the excellent graphics/logging capabilities with real time trend display of many modern bench DMMs.

I am lucky enough to have both 34661A and DMM6500 on my bench. The night I took the picture below I was trying to optimize the cooling of a device I was putting together (the heat came form high-power blue LEDs running in different sequences). I could not find in my drawers any thermistor or temperture sensor my 34661A could read. Luckily, I had a bunch of K-type thermocouples that worked just fine with my DMM6500 (the one particularly used here came with one of my Flukes). Job done.

Might be relevant to some.


Kleinstein:
It can absolutely make sense to use a 6 digit DMM with a thermocouple. The absolute accuracy of the TCs is limited, but the reproducibilty can still be good. All it needs is an external cold junction compensation and than some math (the DMM6500 should be able to do the math as a user programmable function).  One does not really need 6 digits, but may want 1 µV or better resolution for the voltage and this is usually found with 6 digit meters and few 5 digit ones.  There are few dedicated thermometers with comparable resolution and they may cost as much as a 6 digit DMM.

The scanner cards for the DMM6500 may include a cold junction sensor.

mawyatt:
We have 3 KS34465s and a DMM6500. The DMM6500 was acquired when a KS34465 was backordered a year and we forgot to cancel the order when we found a DMM6500 in stock as a replacement (this was our first Keithley Instrument). When the KS arrived a year later we decided to go ahead and keep it since the price had really jumped up!!

Now that we have both types the DMM6500 lower ohms range is highly appreciated, both types are really good instruments and one can't go wrong with either!!

Best,

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